Influence of conditioned natural immunity on tumor growth.

We studied the effect of classical (Pavlovian) conditioning of the natural killer cell response on survival of tumor-bearing mice. Mice were given repeated injections of poly I:C every three days paired with exposure to the odor of camphor for 4 hours. First, we investigated the possible therapeutic effect of repeated exposure to the odor of camphor on the growth of MOPC 104E murine myeloma. The results indicate that camphor alone had no therapeutic effect when the mice were exposed to the odor of camphor after tumor transplantation. We then investigated the effect of repeated exposure to camphor prior to tumor transplantation and subsequent repeated exposure to camphor following tumor transplantation. Again, we observed no therapeutic benefit. In a third experiment, we examined the effect of the conditioned poly I:C response on the growth of the murine myeloma. Animals in the conditioned group had an increase in median survival (day 43, as compared to days 34, 38, 37 of various control groups). Two of these conditioned mice lived more than 120 days and showed early tumor growth, but were free of disease at day 97. During the course of the study conditioned mice received no additional treatment other than being reexposed to camphor every third day.